The 'Bombing of Nagaoka' was a late part of the strategic bombing campaign flown b y the USA against both military and civilian targets and population centres in the Japanese home islands during the closing stages of World War II (1 August 1945).

Nagaoka was a regional commercial centre and the location of one of the laboratories of Japan’s Institute of Physical and Chemical Research, and in 1945 possessed a population of some 67,000 persons. It came to be believed locally that the town had been targeted because it was the home town of Admiral Isoroku Yamamoto, who had directed the 'Ai' attack on Pearl Harbor, but the presence of the chemical laboratory was more likely the reason the city was targeted.

Nagaoka was attacked for the first time on 26 July 1945 as one of the 10 to be attacked late in July by the US Army Air Forces' 509^th Composite Group, commanded by Colonel Paul W. Tibbetts, to practice the tactics the unit later used to undertake the 'Silverplate' and 'Centerboard' atomic bombings of Hiroshima and Nagasaki. These raids were undertaken by small groups of two to six Boeing B-29 Superfortress four-engined bombers armed with 'Pumpkin' bombs, which were aerodynamically identical to the 'Fat Man' A-bomb. The 509^th Composite Group assessed the results of the small attack on Nagaoka as having been 'fair'.

During the night of 27/28 July B-29 bombers dropped leaflets on Nagaoka and 10 other cities. These leaflets stated that they would be subjected to attack, and that civilians should leave. This was a tactic sought to intensify the psychological effects of the bombing campaign.

The main raid on Nagaoka was flown on 1 August 1945. Beginning at about 20.30 that night, 125 B-29 bombers of the Colonel George W. Mundy’s 313^th Bombardment Wing struck the city with an estimated 163,000 incendiary bombs totalling 925 tons in a raid which lasted lasted 100 minutes. The city suffered severe damage, though estimates of its extent vary: in 1953 the USAAF’s official history stated that 65.5% of Nagaoka’s urban area had been destroyed, but in 2016 The Washington Post claimed that 80% of Nagaoka had been burned. Some 1,486 persons were killed in Nagaoka, this figure including more than 280 school-age children. The US which attacked Nagaoka suffered no aircraft losses or personnel casualties.

The cities of Toyama, Mito and Hachioki were also attacked on the night of 1/2 August, and suffered severe damage. The New York Times reported that these raids had included the largest number of bombs dropped up to that time.